Initialism of abdominal aortic aneurysm. • Initialism of aromatic amino acid. • Initialism of anti-aircraft artillery. • Initialism of animal-assisted activity. • Initialism of adult album alternative. • Initialism of advanced acoustic array. • Initialism of Access Approval Authority. • Initialism of accumulated adjustments account, in US Federal Income Tax. • Initialism of adaptive array antenna. • Initialism of airborne assault area. • Initialism of aircraft alert area. • Initialism of airport airspace analysis. • Initialism of angle angle angle, a geometric proof. • Initialism of arrival and assembly area. • Initialism of astronaut-actuated abort. • Initialism of attitude, awareness and accountability, a ski safety program. • Initialism of authentication, authorization and accounting. • Initialism of automated airlift analysis. • Initialism of administration, authorization, and authentication, in software security. • Initialism of AEGIS acquisition agent. • Initialism of aerospace engineering, applied mechanics, and aviation. • Initialism of air avenue of approach. • Initialism of airborne array aperture. • Initialism of allocations, assessments, and analysis. • Initialism of alternate assembly area. • Initialism of authorization accounting activity; authorized accounting activity. • Initialism of Acquisition Approval Authority.